Most common foundation vents are black plastic sliders that are thin and flimsy or a thin aluminum that bends, rusts, and is not very functional. Current thin slider vents are generally unstable without the buildup of mortar around the opening which tends to block the air flow and prevent the slider from sliding and functioning properly.
Current vents also rarely function properly due to improper installation and foundational structure and do not course out with the majority of brick sizes sold residentially.